Catalanoite is an extremely rare secondary sulfate mineral found as an efflorescence in fumarolic environments. Collectors should look for delicate, needle-like white or colorless crystal aggregates that are typically highly soluble in water.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Catalanoite

Hardness: 2
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this catalanoite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch catalanoite with a known reference. Catalanoite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Catalanoite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Catalanoite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: acicular crystals, efflorescent crusts.

Often confused with

Catalanoite vs. its common look-alikes — and how to tell them apart in the field.

mineral

Alunogen

Mohs 1.5-2

How to tell apart: Luster reads vitreous on Catalanoite and silky on Alunogen.

Often found alongside catalanoite

Minerals reported to co-occur with catalanoite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Al₂(OH)₄(SO₄)·5H₂O
Mohs hardness: 2
Density: 1.74 g/cm³
Colors: White Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Acicular Crystals, Efflorescent Crusts
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Volcanic Fumarole Deposits
Typical price: $50-300 per specimen

Where rockhounds find catalanoite

Classic worldwide localities

Grotte di Catalano, Sicily, Italy

Field-hunting tip

Look in volcanic fumarole deposits country — that is the host setting where catalanoite typically forms. If you start seeing gypsum, alunite in float, you are in the right ground. Field specimens usually show a acicular crystals, efflorescent crusts habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify catalanoite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless.

Where is catalanoite found?+

Notable localities include Grotte di Catalano, Sicily, Italy.

How much is catalanoite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like catalanoite?+

Catalanoite is most often confused with Alunogen, Halotrichite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with catalanoite?+

Catalanoite commonly co-occurs with Gypsum, Alunite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does catalanoite form in?+

Catalanoite typically forms in volcanic fumarole deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is catalanoite used for?+

Catalanoite is used in collector.

Find catalanoite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.